Edge guide feed-back system



June 26, 1962 P. ANDERSEN EDGE GUIDE FEED-BACK SYSTEM 3 Sheets-Sheet 1Filed Jan. 8, 1960 June 26, 1962.

Filed Jan. 8, 1960 P. ANDERSEN 5 Sheets-Sheet 2 June 26, 1962 P. ANDERSEN 3,040,944

EDGE GUIDE FEED-BACK SYSTEM Filed Jan. 8, 1960 3 Sheets-Sheet 3Amplifier 24a 23b! ze 263 ,260

-z I Motor I a Pump \42 I? 2|b -cif Fig.6 Lkz "42d F? I 45 l I 56c I xUnite States Patent G 3,040,944 EDGE GUIDE FEED-BACK SYSTEM PoulAndersen, Wallingford, Conn, assignor to The Wallingford Steel Company,Wallingford, Conn, 21 company of Connecticut Filed Jan. 8, 1960, Ser.No. 1,277 3 Claims. (Cl. 226-21) This invention relates to improvementsin edge guide systems and relates in particular to an edge guidefeedback system.

In the manufacture of any continuous strip material, such as stainlesssteel strip or textile web, the material is fabricated into elongatedbands that are subjected to processing steps involving treatment in avariety of mills that involve continuous passing of such strip over andthrough numerous rolls. Examples of such mills are hot rolling mills,cold rolling mills and annealing and pickling lines. When passing oversuch rolls and through such processing apparatus, it is necessary thatthe strip or web travel in a substantially uniform manner so as tominimize variations in properties due to variations in the exactposition of the strip as it passes through heat zones and opposingrolls. The desired predetermined path for the strip to follow isgenerally referred to as the pass line, and various methods have beendevised to maintain such strip as accurately as possible on the passline.

An edge guide as used in industry today is an automatic device thatcontrols the position of a roll (or system of rolls) to maintain a fixedpass line in a continuous processing line for different types of stripor Webs. The edge guide will normally consist of a sensing head, powerunit and roll position unit. The sensing head can be either air orphotoelectric operated, feeding the signal to the power unit where it isamplified. The amplified signal, in most cases, in the form of hydraulicpressure is transmitted to a hydraulic cylinder operating the steeringroll or rolls.

Presently employed edge guides employ a stationary sensing head which isthe main cause of hunting or constant over-correction of the steeringroll. Such hunting results in the strip constantly wavering in and outof the pass line which is an undesirable condition leading to anon-uniform product. Hunting is mainly observed on low speed processinglines where the correction speed is too low for the response of thecontrolling unit. It is, of course, possible to decrease the sensitivityof the controlling unit and arrive at the right relationship betweencorrection speed and sensitivity even at a very low strip speed. Asdescribed in the previous paragraph, there is only one processing speedthat is correct for a certain sensitivity; if the sensitivity of thesystem is too high for the processing speed, hunting will occur; if toolow, the

steering roll will not respond quickly enough and the processed materialwill wander beyond allowed limits. An ideal system is one that possessesa high degree of sensitivity (responds quickly to a deviation in thepass line), but which will not create hunting due to such sensitivity.Such a system would be highly effective regardless of the speed ofprocessing.

The edge guide system of the present invention prevents hunting on lowspeed processing lines while maintaining a high sensitivity on low asWell as high speed lines.

In addition, it is inherent in the prior known edge guide systems thatwhen the mill is, for any reason, brought to a complete stop, thesteering rolls invariably assume a complete correction angle. Such aphenomenon is obviously undesirable since, unless adjustments to therolls are effected prior to starting the mill, the strip will be causedto substantially deviate from the pass line. The

3,040,944 Patented June 26, 1962 edge guide feed-back system of thepresent invention eliminates this difficulty, in that when this systemis employed the mill may be stopped and started without adverselyafiecting the correction angle of the steering rolls.

It is the object of the present invention to provide an edge guidefeed-back system on a strip processing line that will prevent or reducehunting and still maintain a high degree of sensitivity.

It is a further object of the present invention to provide a strip guidefeed-back system wherein the sensitivity of the system need not beadjusted in accordance with the speed of the of the processing mill.

Another object of the present invention is to provide a strip edge guidefeed-back system wherein the strip processing mill may be brought to acomplete stop without effecting an adverse correction angle to thesteering rolls.

Further objects and advantageous features will be ob vious from thefollowing description when taken in conjunction with the accompanyingdrawings in which:

FIGURE 1 is a schematic view in elevation and partly in section of astrip guide apparatus embodying the teachings of this invention;

FIG. 2 is a view in elevation of the strip guide apparatus of FIG. 1,the illustration of FIG. 2 being rotated from the position shown in FIG.1;

FIG. 3 is a view in elevation and partly in section of the strip guideroll assembly 15 of FIG. 1, the illustration of FIG. 3 being rotated 90from the position shown inFIG. 1;

FIG. 4 is a top plan view of the strip guide roll assembly of FIG. 3being partly in section taken along the lines IV-IV of FIG. 3;

FIG. 5 is an enlarged view in elevation and partially in cross sectionof the strip guide and sensing head propelling mechanism 13 of FIG. 1;and

FIG. 6 is a schematic illustration of a sensing device and torqueactuator (in section) that may be employed to control the apparatus ofFIGS. 1 through 5.

In the apparatus of the present invention, the correcting motion of thesteering rolls is, by a mechanical linkage, transmitted to the sensinghead, perpendicular to the strip. This will allow the sensing head,after detecting a shift in the pass line, to follow the edge and satisfyitself with the steering roll in a correcting position. When the stripis returning to the original pass line, a new signal from the sensinghead will actuate the control unit and the steering roll or rolls start[returning to the neutral position; the sensing head will likewise,through the feedback system, return to the original position.

The sensitivity of the guiding system is not related directly to thecorrection speed (a function of strip speed and steering angle) and cantheoretically be as high as desired, limited only by the mechanicalresponse of the roll unit.

The low limit of sensitivity is determined by the maximum correctionspeed versus speed of sensing head in accordance with the formula:

V 1 V cos Y where V Speed of sensing head V -M aximum line speedY-Maximum correction angle The amount of feed-back is determined eitherby maximum anticipated variation in pass line, or the sensitivityrequired for the complete guide system. The smaller the feed-back, thegreater the sensitivity of the system, approaching zero feed-back, Wherethe sensitivity is only dependent on the response of sensing head andcontrol unit. Accordingly, in the system of the present invention, thesensing head is caused to follow the deviating strip during correctionso that the correction is cancelled in anticipation of the return of thestrip to the pass line.

The device of the present invention requires the cooperation andfunctioning of three basic components or units to accomplish the desiredstrip guidance. These units are illustrated generally in FIG. 1 as thesensing head 11 (see also FIG. 2), the strip guide and sensing headpropelling mechanism 13 (see FlG. and the strip guide correction rollassembly (see FIGS. 3 and 4).

The three units '11, 13 and 15 cooperate and function as a single unit.The following description is a broad and general explanation of thefunctions performed by each unit in cooperation with one another, with amore detailed description of the construction and operation of each unitfollowing such broad and general description.

In general, a sensing head 11 is positioned to follow one edge of themetal strip (shown as 17 in FIG. 1) and when there is a deviation of thepath of the strip 17, the sensing head 11 detects such deviation andtransmits this information to the propelling mechanism 13, whichimmediately initiates and applies a corrective force to the strip 17 byadjusting the position of the roll unit 15. In the meantime,simultaneously and in accordance with the present invention, thepropelling mechanism 13 eifects a corresponding adjustment in theposition of the sensing head 11 so as to propel the sensing head '11 inthe same direction as the deviation movement of the strip. By so doing,the senisng head 11 satisfies itself with the edge of the strip 17 soonafter the correction force applied through roll unit 15 takes effect andcommences to return the strip 17 to its correct position. Uponsatisfying itself with the strip edge, the sensing head 11 againtransmits an impulse to the propelling mechanism 13 which cancels thecorrection force applied to the strip by roll unit 15 and effects areturn of the roll unit 15 towards its original position andsimultaneously effects a propelling of the sensing head 11 towards itsoriginal position. Should the'strip fail to return to its accurate,original position but once again commences to deviate, the sensing head11 will detect the variation in position of the edge of the strip and acorrection force will be reapplied, as above, soon after such seconddeviation occurs, since the sensing head 11 will continue to follow theedge of the strip both during the deviation and during the correction.

The sensing head 11, particularly as shown in FIG. 2, is composed of alight source 2.1 and photoelectric detector 23 carried by a suitablesupporting and adjustable positioning structure. The sensing headmechanism itself is well known in the art and is employed in manyindustries wherein strips of material pass over a series of rolls. Thesensing head 11 can be of any suitable type such as the air orphotoelectric cell operated types capable of feeding a signal to thepower unit.

In the present embodiment, there is employed a sensing device and torqueactuator such as is provided by the .Ask-ania Regulator Company ofChicago, Illinois (Askania Regulator No. AL) and the Ex-Cell-OCorporation of Detroit, Michigan (Rotac Model RN-32- 2V). A schematicillustration showing generally the manner in which such a systemfunctions is shown by FIG. 6. A light bulb 21a emits a light which isdirected, by means of a lens 21b, to a second lens 23a which directs thelight to a photocell 23b. Photocell 23b is of conventional manufacture,in the present embodiment being a Photocell RCA7163 (Radio Corporationof America). Such a cell performs its usual function of providing anelectric current, the intensity of which varies in accordance with theamount of light directed toward it by light bulb 21a and lenses 21b and23a. Such current flows through a wire 24 and is amplified by aconventional type amplifier illustrated generally in FIG. 6 by box 26.The amplified electric current flows through a line 26a and a coil 28 toinduce a magnetic force into a core 39. The circuits are completed toamplifier 26 and photocell 23b, respectively, through wires 26b and 24a.Hence, it may be readily seen that the intensity of the electric currentflowing in coil 28 depends on the amount of light emitted by bulb 21aand directed by lens 21b that reaches photocell 23b. It is obvious thatthe magnetic force induced into core 30 also depends on the intensity ofsuch electric current. A steel jet nozzle such as is illustrated at 36is pivotally mounted to a stationary member (not shown) at 38. Amagnetic force of attraction imposed by core 30 tends to pivotallyattract jet nozzle 36; however, this tendency is opposed by a spring 4-0that is attached to the other side of jet nozzle 36 to a stationarymember, in the present embodiment shown to be motor and pump 42. Member36a is an integral part of jet nozzle 36 and serves as an attachmentmember for spring 40 and as a spacer member for magnetic attraction fromcore 30. Jet nozzle 36 is supplied with hydraulic fluid under pressurefrom the motor and pump, shown schematically at 42, through an inlethose 42a. The jet outlet 44 is positioned contiguously with adistributor member 46. The conventional motor and pump 42 supplies fluidpressure to jet nozzle 36 through an inlet hose 42a. Jet outlet 44 issubstantially enclosed in the vicinity of distributor 46 by enclosure42b which confines the fluid force emitted by the jet nozzle 36. Anopening 420 is provided in enclosure 4217 into which jet nozzle 36projects. Opening 420 is of sufficient size to permit pivotal movementof jet nozzle 36 inside the enclosure 42b. Fluid returns to the motorand pump 42 for re-circulation through outlet hose 42d. Distributormember 46 has two outlets 46a and 46b that converge on substantially thesame point contiguous with the jet of hydraulic fluid emitted by nozzle36 when it is in a vertical position. Outlets 46a and 46b lead tohydraulic hoses 43a and 48b which, in turn, lead to torque actuator 47.Torque actuator 47 (shown in cross section in FIG. 6) is composed of twochambers 50 and 52 that are separated by a stationary fin 54 and arotatable fin 58 that is rigidly attached to shaft 49 as by welding,etc. In operation, the tension of spring 40 is so adjusted that when theedge 17:: of strip 17 only blocks half the light emitted by bulb 21adirected by lenses 21b and 23a to photocell 2%, the amplified electriccurrent flowing through the coil 28 is just suflicient to maintainpivotally mounted jet nozzle 36 in a vertical position. When jet nozzle36 is in a vertical position, the jet stream emitted flows equally intopassageways 46a and 46b of distributor member 46. Such hydraulic forceflows through pressure hoses 48a and 48b and into compartments 50 and 52of torque actuator 47. Since these forces (represented by arrows 56a and5612) are equal, they cancel one another and the rotatable fin 58 andhence the shaft 4-9 remain stationary and no correction on thecorrection roll assembly is effected. On the other hand, if the strip 17deviates from the pass line so as to block out or cover more than halfthe light emitted from bulb 21a and directed by lens 21b to photocell23b, the electric current in lines 24 and 24a and, hence, the current incoil 28 is appropriately diminished; consequently, the magnetism inducedinto core 30 is diminished. As a result of the diminished magneticattraction imposed by core 30 on jet nozzle 36, spring 40 overcomes theattraction to the degree the electric current was diminished and jetnozzle 36 is pivotally moved in the direction of spring 40 and a greateramount of the hydraulic fluid jet stream is directed toward passageway46a than 46b so that greater hydraulic pressure flows in hose 48a thanin 48b and the pressure in chamber 52 of torque actuator 47 becomesgreater than that in chamber 50 and the fin 58 is caused to rotate inthe direction shown by the arrow 56a which causes rotation of shaft 49to effect a correction angle to correction roll unit 15 as will behereinafter described in detail.

page

The hydraulic pressure directed by jet nozzle 36 that ultimately effectsgreater hydraulic pressure in chamber 52 continues until the correctionhas taken effect and the sensing head 11 has satisfied itself with thestrip edge 17a in which event the amount of the light emitted by bulb21a and that is received by photocell 23]) provides an electric currentto eifect the necessary magnetic attraction in core 30 to oppose spring40 and position jet nozzle 36 in a vertical position. With jet nozzle 36in a vertical position, as shown above, the pressure in chamber 50becomes equal to that in chamber 52 of torque actuator 47 and theopposing hydraulic forces 56a and 56b cancel one another. If strip 17deviates from the pass line in such a manner as to cause a greaterportion of the light emitted from bulb 21a and directed by lenses 21band 23a to reach photo-cell 231), a greater electric current will flowthrough coil 23, hence a magnetic force is induced into core 30 thatwill overcome the spring 40 to the eX- tent of the deviation of strip17. In this event, the jet stream emitted by jet nozzle 36 will bedirected in the direction of passageway 46b of distributor 46 and agreater hydraulic force will result in chamber 50 than chamber 52 oftorque actuator 47. In this event, fin 58 and hence shaft 49 of torqueactuator 47 will be revolved in the direction indicated by the arrow 56band a correction of roll unit 15 will be effected in a reverse directionto that previously described. When strip 17 responds to the correctionforce, the light emitted by bulb 21a and directed to photocell 23b bylens 21b will be diminished effecting a diminished electrical current incoil 23 and hence reducing the magnetic attraction of core 30 to permitjet nozzle 36 to return towards its vertical position or to once againeffect a greater hydraulic force in cham ber 52 of torque actuator 47.

Adjacent to torque actuator 47 as shown in the schematic illustration ofFIG. 6, there is shown, for illustrative purpose, a schematic top Viewof a roll unit 15. As will be shown in detail, rotation of shaft 49 oftorque actuator 47 effects a pivotal movement of roll unit 15 aboutpivot 131 as shown by the double arrow 15a.

The mechanism of the present embodiment is designed specifically for theprocessing of heated steel strip so that special precautions must betaken to protect the equipment from the heat emitted from the metal andthe annealing furnace.- For example, the photoelectric detector 23 andthe light source 21 of sensing head 11 are water cooled. Cooling wateris supplied to these members through members 25 and 27 (see FIG. 2)which are metal tubes that serve as water inlets and outlets,respectively, as Well .as supporting members for these components.Members 25 and 27 are mounted on a vertical supporting member 29 whichis, in turn, rigidly mounted on a movable platform 33 that is part ofthe propelling mechanism 13 (described hereinafter in greater detail).Cooling water is supplied and drained from tubular members 25 and 27through hose connections (not shown) leading from a convenient source ofwater and to suitable drains. Diagonal supporting member 31 lendsadditional support to vertical supporting member 29 and is attached tomember 29 and to a plate 32 as by welding, etc. Plate 32 is bolted toplate 117 of platform 33, as shown in FIG. 1, bybolts 34 and nuts 34a.Supporting member 29 is also bolted (not shown) to platform 33 in amanner similar to that of diagonalsupporting member 31.

Additional protection from a possibly broken strip is provided by aprotector plate 35 mounted on a supporting member 37. Protector plate 35is formed with a slot 39 through which the light from light source 21may be projected to the photoelectric detector 23.

The over-all unit, as shown in FIGS. 1 and 2, including propellingmechanism 13 and roll unit 15, is supported by inverted U-shaped beams41 and sensing head 11 is movably supported, as will hereinafter bedescribed, on inverted U-shaped beam 43.

The sensing head 11 is so positioned that the steel strip 17, whilecorrectly positioned in the processing line, runs so that its edge is inthe center of the light beam emitted from light source 21 and passing tophotoelectric detector 23 so that deviation in the path of travel orpass line of the strip 17 in the directions indicated by double arrow 45in FIG. 2 will cause a variation in the light intensity received byphotoelectric detector 23. Such variation, as previously described,effects a hydraulic pressure in torque actuator 47 that, in turn,eifects a correction angle to correction roll unit 15.

The propelling mechanism 13 is composed of the positioning torqueactuator 47 which provides the predetermined motivating force forpositioning the roll unit 15 and additionally for the sensing head 11.The torque actuator 47, as described above, effects rotation of a driveshaft 49 when actuated by hydraulic pressure. Torque actuator 47 isprovided with a flange 61 that is rigidly attached as by welding orbolting to attachment plate 61a. Flange 61 of torque actuator 47 andattachment plate 61a are, in turn, rigidly attached as by bolting orwelding to supporting members 63, 65 and plate 67 which are welded orbolted together to form a rigid b-oxlike structure that providesadequate support for the torque actuator 47 and other componentshereinafter described.

Rotation of drive shaft 49 effects a swinging motion of forked arm 51(see FIG. 3) that is received on the upper end thereof. Riding in theslot of the forked arm 51 is a rotating cam follower 53 that is attachedto the roll unit base 55 through a rigidly attached plate 57.

The roll unit base 55 itself is rotatably mounted to supporting member65 through a pivot 131. Pivot 131 is composed of an upwardly projectingcylindrical member 132 that is rigidly attached to supporting member 65,as by welding, etc., and which projects into a cylindrical bearingreceptacle 134 that is rigidly attached at one end of the unit base 55,as by welding, etc. Thrust washers 133 surrounding cylindrical member132 prevent the roll unit base 55 and cylinder 134 from bearing directlyon support member 65 when the roll unit base 55 rotates about pivot 131.The unit base 55 is additionally sup-.

ported by two cam followers 139 and 139a that are rigidly mounted onsupporting member 65 by means of supporting members 141. The camfollowers 139 and 139a support and engage bearing plate 137 that isrigidly attached, as by Welding, etc, to an angle beam 135 that is inturn rigidly attached, as by Welding, etc., to the unit base 55. Anglebeam 144, which is also rigidly attached to the unit base 55 andprojects outwardly beneath the rotatable cams 139 and 139a, acts as aguide member for the unit base 55.

It may be seen that rotation of shaft 49 by actuator 47 effects aswinging motion to forked arm 51 which, in turn, bears on cam 53 toeffect a swinging motion to the unit base 55' about pivot 131. Bearingplate 137 is supported and effects rotation of cams 139 and 139aduringsuch motion. Since shaft 49 turns for only a predetermined degree, thecorrection angle elfected on roll 127 by pivotal motion of unit base 55about its pivot 131 is also predetermined.

The correction roll itself is, of course, a conventional drive roll 127mounted on a plate 157 that is rigidly attached, as by welding, etc., tothe unit base 55. This roll assembly is composed of an idler roll 127mounted on a shaft 147 that is rotatably mounted in bearing members 151assembled in clamp members 149.. Clamp members 149 are bolted to plate157 by bolts 155 that project through both the flanges of members 149and the plate 157.

Referring to FIG. 5, it isnoted that the drive shaft 49 of the torqueactuator 47 and another shaft 71 project downwardly from the lower endof the torque actuator through an opening 70 formed in plate 61a andplate 67 of the general boxlike structure formed by members 63 and 65and supporting member 66 that serve. as support for the over-allstructure. Shaft 71 is in alignment with and is keyed to shaft 49 asshown by the dotted lines at 72 so that shaft 71 rotates with shaft 49.A seamless coupling 73 is disposed around the keyed junction 72 ofshafts 71 and 49 and is rigidly affixed by set screw 72a to the shaft,and hence rotates when shaft 49 and shaft 71 rotate. The function ofcoupling 73 is, of course, to connect the two shafts 49 and 71 and toprovide a thrust bearing support therefor when seated on the flange ofbushings 77. A flanged seamless tube 76 surrounds the shaft 71 and actsas a housing for bushings 77 as well as a supporting member therefor. Itis noted that tube 76 is flanged at its upper end as shown at 76a and isbolted through spacer 78 to torque actuator base plate 67 by bolts 74and 74a. Bronze bushings 77 are disposed about the opposite ends of theflanged seamless tube '76 to provide bearing surfaces for shaft 71 andtube 73 (which rotates with shafts 49 and 7'1).

A forked arm 79 is afiixed to the lower end of shaft 71 at 71:: as bymeans of welding with the slotted portion of the arm 79 engaging arotatable cam follower 81 disposed therein. The cam follower 81 issecured to a slotted arm 87 by a nut 85. The slotted arm 87 ispositioned horizontally below the roll unit 15 and the positioningtorque actuator 47 (see FIG. 1) and projects outwardly therefrom tobeneath the movable platform 33 on which sensing head 11 is mounted. Arm87 is provided with an undercut slot 89, as shown in FIG. 5, that runshorizontally from one end thereof for about /1 of its length.

In order to control the degree of movement of the platform 33 inresponse to a movement of the power unit 47, the slotted arm 87 ismounted on an adjustable cam follower 91 which functions as a pivot forthe arm 87. Thus rotation of shafts 49 and 71 imposed by torque actuator47 effects a swinging motion to forked arm 79 and such motion will causea pivotal motion of slotted arm 87 about the cam follower 91 which ridesin the slot 89 of arm 87. Brass plate 88 is rigidly attached to supportbeam 94 and provides support to arm 87 which slides over this member.The cam follower 91 is adjustably mounted in a slotted channel 92 formedin a support beam 94 by means of spaced plates 95 disposed on oppositesides of slotted beam 94 and secured together as by means of the shaft91a of cam follower 91 and a nut 99. Thus, the cam follower 91 may beadjusted horizontally along the arm 87 by loosening the nut 99, which inturn permits adjustable motion of the clamp by loosening the clampingforce of plates 95 on the slotted channel 92 of beam 94. Horizontaladjustment of cam follower 91 relative to the arm 87 affects the amountof travel of platform 33 and hence, sensing unit 11 along the fixedrails 125. On the other end of the slotted arm 87, there is mounted anannular flange 101 that is rigidly attached to the arm 87 by means ofbolts 103. A stud shaft 105 projects to the center of annular flange 101and is welded thereto to provide a rigid mounting. A seamless tube 107'is disposed about the shaft 105 with hearing bushings 109 disposedtherebetween, such assembly being secured in assembled position as bymeans of the nut 113 on the threaded head 111 of the shaft 105. Thus,relative rotative movement is obtained between the shaft 105 and thetube 107 as the arm 87 swings about cam follower 91. The tube 107 isrigidly attached by welding 107a to the movable platform 33 carryingsensing device 11. The movable platform 33 is composed of side members112, a bottom plate 115 and a top plate 117, all of which are rigidlyattached together, as by welding, etc. Bottom plate 115 is rigidlyattached to seamless tube 107 by welding. Four spaced 'cam followers 123are attached to opposed side members 112 by means of their shaftsprojecting through holes in plates 112 (not shown) and nuts 12 1. Camfol-f lowers 12.3 are disposed to bear on associated rails 125 that arerigidly attached as by welding to supporting beam 43. Rails 125 arerigidly attached to supporting beam 43 by means of bolts 125w.Supporting beam 43 is shown in the present embodiment to be rigidlyattached to upwardly projecting supporting member 37 (see FIG. 2) on oneend and is attached to a similar member on the other end (not shown).Thus, it may be observed that rotation of shafts 49 and 71 by torqueactuator 47 effects a swinging motion to forked arm 79 that bears on cam81 to cause a pivotal swinging motion to arm 87 about cam follower 91that effects corresponding propulsion to movable platform 33 throughshaft 105, hence effecting a propelling of the sensing unit 11 along therails in the same direction as the deviation of the strip 17 in thedirection shown by the double arrows 45 of FIG. 2. Such motion has beeneffected simultaneously with the swinging motion of forked arm 51 which,as shown above, imparts a correction angle movement to roll 127.

Thus, it is seen that variation of the beam of light emitted by lightsource 21 directed to photoelectric detector 23 of sensing head 11 bythe strip 17 deviating from the pass line in either direction shown bythe double arrow 45 of FIG. 2 effects a predetermined correctionrotation of shaft 49 by torque actuator 47. Such rotation in turneffects a swinging motion of forked arm 51 on the upper end and forkedarm 79 on the lower end through connecting shaft 71. While forked arm 51swings and effects a correcting angle to the roll 127 by pivotal motionof the unit roll base 55 pivoting on pivot 131, forked arm 79 effects apivotal motion of slotted arm 87 due to the effect of cam follower 81 inthe slot of forked arm 79 and consequently through shaft 105, which isrigidly attached to the other end of arm 87, effects correspondingpropulsion to movable plat form 33, thus effecting a movement of thelight source 21 and photoelectric detector 23, due to the movement ofthe platform 33, in the direction 45 of the deviating strip. It is alsoapparent that when the correcting angle of roll 127 commences to effecta return of the strip 17 to the correct position of the pass line, thelight beam emitted by light source 21 and directed to photoelectricdetector 23 will be re-established. Since the sensing device 11 followedthe edge of the strip 17, it will reengage the edge much sooner than ifit had remained stationary. Upon re-establishment of the balanced beam,the torque actuator 47 is activated to return sensing unit 11 to itsoriginal position, and simultaneously returns the roll 127 to itsinitial position. The shaft 49 rotates to its original position andeffects a return of forked arm 51 to its original position and hence,cam follower 53 causes pivotal motion of the unit base 55 about pivotalconnection 131 to return the base to its original position.Simultaneously, shaft 49 effects rotation of shaft 71 to its originalposition, causing a reverse effect on forked arm 79 and cam follower 81,pivotally swinging arm 87 about cam follower 91 to its original positionwhich, in turn, effects a return of the movable base 33 carrying thesensing unit 11, and causing the light beam emitted from source 21 tophotoelectric detector 23 to follow the strip back.

If the edge guide feed-back system was not employed and the sensing head11 was fixed in a stationary position, then the system would beillustrative of the prior known edge guide systems. It can be seen thatif such were the case and the strip mill were stopped during any periodwherein the edge 17a of strip 17 varied even very slightly from the passline, which for practical purposes is always the case, the current incoil 28 (see FIG. 6) would be affected and jet nozzle 36 would not be inan absolutely vertical position. From the above, it is readily seen thatthis will cause a greater hydraulic force in one of the chambers 59 or52. Since the correction angle consequently imposed cannot be reversedor stopped because the strip is stopped and there is no response to thecorrection angle imposed, the steering rolls will ultimately effect afull correction angle no matter how small the hydraulic pressure variesbetween the two chambers 50 and 52.

It is readily seen that by employing the edge guide feed-back system ofthe present invention this phenomenon does not occur. When the mill orstrip has stopped moving, the feedback system will function as usual sothat the sensing head 11 Will satisfy itself as to the edge of strip 17so that the light emitted by bulb Zia and directed by lens 21b thatarrives at photocell 2312 will be precisely the amount required toeffect that electric current in coil 28 that will result in a magneticattraction by core 30 to oppose spring 40 and maintain jet nozzle 36 ina vertical position. Thus, the hydraulic pressure in chambers 50 and 52will be the same and no further correction angle will be imposed on thesteering roll 127.

I claim:

1. In a strip guide apparatus wherein a sensing head is disposed tofollow one edge of the strip and upon deviation of said strip from itspass line effect a signal to a torque actuator that is disposed toeffect rotation of a vertically positioned shaft in response to saidsignal that in turn eifects a correction angle to a steering roll overwhich said strip passes to eifect a return of said strip to said passline and said sensing head being further disposed to effect a signal tosaid torque actuator to effect a reverse rotation of said shaft tocancel the correction angle of said steering roll upon the return ofsaid strip to said pass line, the improvement in combination therewithcomprising, a horizontally positioned arm formed with a longitudinalslot and disposed to pivot about a fixed cam projecting into said slot,a forked arm attached to said shaft and disposed to swing in ahorizontal plane upon rotation of said shaft, a cam rigidly attached toone end of said horizontally positioned arm disposed to project into thefork of said forked arm, a movable platform on which said sensing headis mounted, said platform being disposed to travel on a predeterminedpath and said platform being rotatably connected to the remaining freeend of said horizontally positioned ann so that a swinging motion ofsaid forked arm will effect pivotal motion of said horizontallypositioned arm through said cam Within the fork of said forked arm andabout said fixed cam projecting into said longitudinal slot formed insaid horizontally positioned arm, such pivotal motion being transmittedto said platform through said rotatable connection to effect travel ofsaid sensing head corresponding to the correction angle effected in saidsteering roll by said shaft so that said sensing head will travel in thedirection of said deviation during said deviation and in the directionof return during said return.

2. In a strip guide apparatus wherein a sensing head is disposed tofollow one edge of the strip and upon deviation of said strip from itspass line effect a signal to a torque actuator that is disposed toeffect rotation of a vertically positioned shaft in response to saidsignal that in turn effects a correction angle to a steering roll overwhich said strip passes to effect a return of said strip to said passline and said sensing head being further disposed to effect a signal tosaid torque actuator to effect a reverse rotation of said shaft tocancel the correction angle of said steering roll upon the return ofsaid strip to said pass line, the improvement in combination therewithcomprising, a horizontally positioned arm formed with a longitudinalslot and disposed to pivot about a fixed cam projecting into said slot,means for adjusting the fixed position of said cam so that the pivotalmotion of said horizontal positioned arm about said fixed cam can bevaried, a forked arm attached to said shaft and disposed to swing in ahorizontal plane upon rotation of said shaft, a cam rigidly attached toone end of said horizontally positioned arm disposed to project into thefork of said forked arm, a movable platform on which said sensing headis mounted,

said platform being disposed to travel on a predetermined path and saidplatform being rotatably connected to the remaining free end of saidhorizontally positioned arm so that a swinging motion of said forked armwill effect pivotal motion of said horizontally positioned arm throughsaid cam within the fork of said forked arm and about said fixed camprojecting into said longitudinal slot formed in said horizontallypositioned arm, such pivotal motion being transmitted to said platformthrough said rotatable connection to effect travel of said sensing headcorresponding to the correction angle effected in said steering roll bysaid shaft and the amount and speed of said travel depend ing on thefixed position of said fixed cam so that said sensing head will travelin the direction of said deviation during said deviation and in thedirection of return during said return.

3. In a strip guide apparatus wherein a sensing head is disposed tofollow one edge of the strip and upon deviation of said strip from itspass line effect a signal to a torque actuator that is disposed toefiect rotation of a vertically positioned shaft in response to saidsignal that in turn eifects a correction angle to a steering roll overwhich said strip passes to effect a return of said strip to said passline and said sensing head being further disposed to effect a signal tosaid torque actuator to effect a reverse rotation of said shaft tocancel the correction angle of said steering roll upon the return ofsaid strip to said pass line, the improvernent in combination therewithcomprising, a hori zontally positioned arm formed with a longitudinalslot and disposed to pivot about a fixed cam projecting into said slot,an elongated member horizontally positioned beneath said slotted armsaid elongated support member being formed with a slotted channel,clamping means attached to said fixed cam and disposed to clamp to saidelongated member within said slotted channel, a forked arm attached tosaid shaft and disposed to swing in a horizontal plane upon rotation ofsaid shaft, a cam rigidly attached to one end of said horizontallypositioned arm disposed to project into the fork of said forked arm, amovable platform on which said sensing head is mounted, said platformbeing disposed to travel on a predetermined path and said platform beingrotatably connected to the remaining free end of said horizontallypositioned arm so that a swinging motion of said forked arm will effectpivotal motion of said horizontally positioned arm through said camwithin the fork of said forked arm and about said fixed cam projectinginto said longitudinal slot formed in said horizontally positioned arm,such pivotal motion being transmitted to said platform through saidrotatable connection to eifect travel of said sensing head correspondingto the correction angle effected in said steering roll by said shaft andthe amount and speed of said travel depending on the fixed position ofsaid fixed cam so that said sensing head will travel in the direction ofsaid deviation during said deviation and in the direction of returnduring said return.

References Cited in the file of this patent UNITED STATES PATENTS2,632,642 Cooper Mar. 24, 1953 2,709,588 Staege May 31, 1955 2,716,026Axworthy Aug. 23, 1955 2,735,630 ZiebolZ Feb. 21, 1956 2,782,030 Websteret al Feb. 19, 1957 2,842,361 Miller July 8, 1958 2,928,409 Johnson eta1 Mar. 15, 1960 FOREIGN PATENTS 410,859 Great Britain May 28, 1934762,837 Great Britain Dec. 5, 1956 1,151,045 France Aug. 19, 1957

